Bearings of the type contemplated by the art to which the present invention relates are typically utilized to reduce frictional forces operating at the interface between moving parts. A typical bearing design includes a concave-outward inner race mounted upon a shaft, a concave-inward outer race mounted within a housing concentrically about the inner race, and a number of lubricated round members, such as balls, cylinders, or cones, placed in the space between the inner and outer races. In such a design, the interface between parts moving relative to each other is reduced from a full face contact to a point or line contact, so the frictional forces are reduced based upon the difference between sliding friction (as with full face contact) and rolling friction.
One key to maintaining this reduction of friction at the interface is in preventing slippage, or relative movement between the inner race and the shaft, and the outer race and the housing. Indeed, slippage is one of the principal problems associated with proper bearing design and implementation, and its root cause is an insufficient frictional force between the races and their mating parts. A number of conditions contribute to slippage at the interface. For example, dissimilarities in the material of the bearing and the shaft or housing, and particularly dissimilarities in expansion rates between those materials, can cause imperfect contact between the races and their mating parts, reducing the friction therebetween and resulting in slippage. A second category of causes relates to manufacturing procedures; loose manufacturing tolerances, out-of-round conditions in the housing or the shaft, a lack of concentricity of the races and the housing or shaft, and other irregular conditions result in slippage (or other undesirable operating conditions) because the contact between the races and their mating parts is imperfect.
Irrespective of the cause, such undesirable operating conditions are intolerable primarily for two reasons. First, during operation of the device incorporating, for example, out-of-found or non-concentric conditions, vibration and noise are generated, frequently at undesirable levels. Such vibration and noise, being symptomatic of a failure to achieve the purpose to which bearings are directed, can result in premature failure of the borne parts. Second, slippage (and the heat generated by friction) will usually result in premature failure of the bearing, which in turn causes downtime for repair or, in more serious cases, catastrophic failure leading to machine damage or unsafe operating conditions.
The usual solution to slippage associated with material dissimilarities and loose tolerances is to interpose a mounting ring, which may include a locking device or some frictional material, between the race and its mating part. This ring is typically made of stamped, pressed, corrugated, rolled, cast, or machined metal, adhesive, or molded plastic or synthetic material, and is designed to fit by interference or compression between the race and its mating part. Ideally, the device is designed to accommodate, yet to be resilient against, a compressive force. Assuming that the fit is sufficiently tight to generate a holding force when the bearing and ring are inserted into or onto the mating part, the static friction between the race and the mating part is dramatically increased, and the potential for slippage is correspondingly reduced.
However, the conventional solution is lacking in that it potentially creates at least two additional manufacturing problems. First, the placement of a mounting ring upon the bearing or mating part requires an additional manufacturing step, because in order to be effective the mounting rings (particularly metal rings) are preferably sized too large to maintain themselves upon conventional bearings. Second, housings and shafts must be sized appropriately to accommodate additional material, and the addition of a mounting ring to a bearing design may increase overall design and manufacturing costs because the mating parts may have to be redesigned, or nonstandard bearing sizes may have to be used.
What is needed, therefore, is a bearing that may be preloaded with a mounting ring that effectively compensates for loose tolerances, misalignment, and differential expansion, and a bearing having substantially the same size profile and bearing capacity and characteristics as a standard bearing, but preloaded with a mounting ring.